б) \(\frac{7}{8}-\frac{5}{6}\); г) \(5-3\frac{2}{7}\); е) \(\frac{5}{8}:\frac{9}{10}\); з) \(6\frac{3}{5}\cdot10\).

1. \(\frac{7}{8}-\frac{5}{6}=\frac{21}{24}-\frac{20}{24}=\frac{1}{24}\).

2. \(5-3\frac{2}{7}=5-\frac{23}{7}=\frac{35}{7}-\frac{23}{7}=\frac{12}{7}=1\frac{5}{7}\).

3. \(\frac{5}{8}:\frac{9}{10}=\frac{5}{8}\cdot\frac{10}{9}=\frac{50}{72}=\frac{25}{36}\).

4. \(6\frac{3}{5}\cdot10=\frac{33}{5}\cdot10=66\).

Ответ: б) \(\frac{1}{24}\); г) \(1\frac{5}{7}\); е) \(\frac{25}{36}\); з) \(66\).